so as you know the first spirit weapon we recieve is called “eagles patrimony”
it has lightning themed attacks and you know what else shows lightning in greek mythology? an eagle, the symbol of zeus. what does patrimony mean? its basically a fancy smancy way of saying family heirloom.
this can only mean that were some sort of descendant of zeus giving us spirit energy which allows us to use spirit weapons.
so what does this mean?
we can most likely use a spirit weapon for each magic, for example the wood spirit weapon would be made by Pan, the god of wood or whatever. this is also confirmed to be a later spirit weapon in the dark sea trello page.
so, what about most of the lost and ancient magics that have barely any correlation with greek mythology, like theres no “god of apocalypse bringer”
it would most likely be depending on whichever magic x ancient/lost will come from, for example. the “inferno” magic spirit weapon would originate from either the spirit weapon of prometheus or hephaestus and the death spirit weapon could originate from thanatos or from nyx.
TLDR, each spirit weapon will have a magic counterpart for each magic, for example the earth spirit weapon would come from gaia the god of earth/nature
To add on to what mr_hyperspace said any similarities between spirit weapons and magics will be because the domain of the god and the magic are similar by coincidence. It seems that spirit weapons will produce more natural effects while magic only creates imitations of elements/concepts made of magic energy
there are 3 more planned spirit weapons from what i know
Crystal orb (blessed by aether)
Staff of nyx (blessed by nyx)
Ancient wood in shape of staffs and wands (blessed by Pan)